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$Id: dwarf_child.3 3644 2018-10-15 19:55:01Z jkoshy $
.Dd December 21, 2014 .Dt DWARF_CHILD 3 .Os .Sh NAME .Nm dwarf_child , .Nm dwarf_offdie , .Nm dwarf_offdie_b , .Nm dwarf_siblingof , .Nm dwarf_siblingof_b .Nd retrieve DWARF Debugging Information Entry descriptors .Sh LIBRARY .Lb libdwarf .Sh SYNOPSIS n libdwarf.h .Ft int .Fn dwarf_child "Dwarf_Die die" "Dwarf_Die *ret_die" "Dwarf_Error *err" .Ft int .Fo dwarf_offdie .Fa "Dwarf_Debug dbg" .Fa "Dwarf_Off offset" .Fa "Dwarf_Die *ret_die" .Fa "Dwarf_Error *err" .Fc .Ft int .Fo dwarf_offdie_b .Fa "Dwarf_Debug dbg" .Fa "Dwarf_Off offset" .Fa "Dwarf_Bool is_info" .Fa "Dwarf_Die *ret_die" .Fa "Dwarf_Error *err" .Fc .Ft int .Fo dwarf_siblingof .Fa "Dwarf_Debug dbg" .Fa "Dwarf_Die die" .Fa "Dwarf_Die *ret_die" .Fa "Dwarf_Error *err" .Fc .Ft int .Fo dwarf_siblingof_b .Fa "Dwarf_Debug dbg" .Fa "Dwarf_Die die" .Fa "Dwarf_Die *ret_die" .Fa "Dwarf_Bool is_info" .Fa "Dwarf_Error *err" .Fc .Sh DESCRIPTION These functions are used to retrieve and traverse DWARF Debugging Information Entry (DIE) descriptors associated with a compilation unit. These descriptors are arranged in the form of a tree, traversable using .Dq child and .Dq sibling links; see .Xr dwarf 3 for more information. DWARF Debugging Information Entry descriptors are represented by the .Vt Dwarf_Die opaque type.
p Function .Fn dwarf_child retrieves the child of descriptor denoted by argument .Ar die , and stores it in the location pointed to by argument .Ar ret_die .
p Function .Fn dwarf_siblingof retrieves the sibling of the descriptor denoted by argument .Ar die , and stores it in the location pointed to by argument .Ar ret_die . If argument .Ar die is NULL, the first debugging information entry descriptor for the current compilation unit will be returned. This function and function .Fn dwarf_child may be used together to traverse the tree of debugging information entry descriptors for a compilation unit.
p Function .Fn dwarf_siblingof_b is identical to the function .Fn dwarf_siblingof except that it can retrieve the sibling descriptor from either the current compilation unit or type unit. If argument .Ar is_info is non-zero, the function behaves identically to function .Fn dwarf_siblingof . If argument .Ar is_info is zero, the descriptor referred by argument .Ar die should be associated with a debugging information entry in the type unit. The function will store the sibling of the descriptor in the location pointed to by argument .Ar ret_die . If argument .Ar is_info is zero and argument .Ar die is .Dv NULL , the first debugging information entry descriptor for the current type unit will be returned.
p Function .Fn dwarf_offdie retrieves the debugging information entry descriptor at global offset .Ar offset in the .Dq .debug_info section of the object associated with argument .Ar dbg . The returned descriptor is written to the location pointed to by argument .Ar ret_die .
p Function .Fn dwarf_offdie_b is identical to the function .Fn dwarf_offdie except that it can retrieve the debugging information entry descriptor at global offset .Ar offset from either of the .Dq .debug_info and .Dq .debug_types sections of the object associated with argument .Ar dbg . If argument .Ar is_info is non-zero, the function will retrieve the debugging information entry from the .Dq .debug_info section, otherwise the function will retrieve the debugging information entry from the .Dq .debug_types section. The returned descriptor is written to the location pointed to by argument .Ar ret_die . .Ss Memory Management The memory area used for the .Vt Dwarf_Die descriptor returned in argument .Ar ret_die is allocated by the .Lb libdwarf . Application code should use function .Fn dwarf_dealloc with the allocation type .Dv DW_DLA_DIE to free the memory area when the .Vt Dwarf_Die descriptor is no longer needed. .Sh RETURN VALUES These functions return the following values: l -tag -width ".Bq Er DW_DLV_NO_ENTRY" t Bq Er DW_DLV_OK The call succeeded. t Bq Er DW_DLV_ERROR The requested operation failed. Additional information about the error encountered will be recorded in argument .Ar err , if it is not NULL. t Bq Er DW_DLV_NO_ENTRY For functions .Fn dwarf_child , .Fn dwarf_siblingof and .Fn dwarf_siblingof_b , the descriptor denoted by argument .Ar die did not have a child or sibling.
p For functions .Fn dwarf_offdie and .Fn dwarf_offdie_b , there was no debugging information entry at the offset specified by argument .Ar offset . .El .Sh EXAMPLES To retrieve the first DWARF Debugging Information Entry descriptor for the first compilation unit associated with a .Vt Dwarf_Debug instance, and to traverse all its children, use: d -literal -offset indent Dwarf_Debug dbg; Dwarf_Die die, die0; Dwarf_Error de; ... allocate dbg using dwarf_init() etc ... if (dwarf_next_cu_header(dbg, NULL, NULL, NULL, NULL, NULL, &de) != DW_DLV_OK) errx(EXIT_FAILURE, "dwarf_next_cu_header: %s", dwarf_errmsg(de)); /* Get the first DIE for the current compilation unit. */ die = NULL; if (dwarf_siblingof(dbg, die, &die0, &de) != DW_DLV_OK) errx(EXIT_FAILURE, "dwarf_siblingof: %s", dwarf_errmsg(de)); /* Get the first child of this DIE. */ die = die0; if (dwarf_child(die, &die0, &de) != DW_DLV_OK) errx(EXIT_FAILURE, "dwarf_child: %s", dwarf_errmsg(de)); /* Get the rest of children. */ do { die = die0; if (dwarf_siblingof(dbg, die, &die0, &de) == DW_DLV_ERROR) errx(EXIT_FAILURE, "dwarf_siblingof: %s", dwarf_errmsg(de)); } while (die0 != NULL); .Ed .Sh ERRORS These functions may fail with the following errors: l -tag -width ".Bq Er DW_DLE_DIE_NO_CU_CONTEXT" t Bq Er DW_DLE_ARGUMENT Arguments .Ar dbg , .Ar die or .Ar ret_die were NULL. t Bq Er DW_DLE_DIE_NO_CU_CONTEXT Argument .Ar dbg was not associated with a compilation unit. t Bq Er DW_DLE_NO_ENTRY The descriptor denoted by argument .Ar die had no child or sibling, or there was no DWARF debugging information entry at the offset specified by argument .Va offset . .El .Sh SEE ALSO .Xr dwarf 3 , .Xr dwarf_errmsg 3 , .Xr dwarf_get_die_infotypes_flag 3 , .Xr dwarf_next_cu_header 3